Y Zhong¹, X Hu¹, H Liu²*, Y Lai³, C Shen¹, X Jia¹, (1) UT Southwestern Medical Center, Dallas, TX, (2) Fox Chase Cancer Center, Philadelphia, PA, (3) University of Texas at Arlington, Arlington, TX

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  H Liu

SU-K-202-5 (Sunday, 7/10/2022) 5:00 PM - 6:00 PM [Eastern Time (GMT-4)]

Room 202

Purpose: Preclinical radiation research on small animals pivots the discovery of novel radiotherapy techniques. This work presents the progress of developments on a novel multi-energy cone beam CT (CBCT)-guided intensity-modulated small-animal irradiation platform.

Methods: The developments were based on a customized commercial SmART+ irradiation platform. We improved the imaging quality of the flat panel detector (FPD) CBCT system by performing additional calibration, correction and focal-spot deconvolution. A multi-energy element-resolved (MEER) CBCT algorithm was developed to derive images of electron density and compositions of major elements based on CBCT data acquisitions with multiple gantry rotations with different kVps. We also installed a photon-counting detector (PCD) on the gantry and calibrated the detector for multi-energy CBCT data acquisition in a single scan. Intensity-modulation radiation delivery (IMRD) was implemented by attaching a motorized rectangular collimator. A software system was developed to generate plans based on a Direct Aperture Optimization algorithm with Monte Carlo-based dose calculations.

Results: The additional calibrations of FPD-based CBCT reduced CT number mean error from 19% to 5%. Results of MEER-CBCT on a micro-CT calibration phantom showed that median errors in H, O, Ca fractions and electron density for all the inserts were <1%, 2%, 4% and 5%, respectively. Subsequent Monte Carlo dose calculation showed improved accuracy particularly with the mean dose error reduction from 47.5% to 10.9% in bone regions. IMRD was compared to conformal radiation delivery with fixed-sized collimator. The plan of a C-shaped target around a round organ was delivered and the dose distribution was measured using films. IMRD reduced organ D50% from 88% to 29% after normalization. Measured dose distribution agreed with calculation within 5% mean difference.

Conclusion: Preliminary studies demonstrated potential of accurate dose delivery on the new small-animal irradiation platform with advanced imaging and delivery functions.

Funding Support, Disclosures, and Conflict of Interest: NIH NCI R37CA214639

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